Checking the Power Supply for the Control Unit: VW 2.3 (AGL)

Special tools, testing and measuring devices, etc. required

Fault output device V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/5
Test box V.A.G 1598/26
Hand-held multimeter V.A.G 1526 or Multimeter V.A.G 1715
Measuring aids set V.A.G 1594
Current flow diagram

Testing conditions

Battery voltage at least 11.0 V
Alternator OK, Check:

=> Current flow diagrams, Electrical fault finding and Fitting locations

Testing Procedure

Connect the fault output device V.A.G 1551 and use the "Address word" 81 to select the control unit for engine electronics. Here, the engine must be idling.
(Connect the fault output device and select the control unit for engine electronics => Page
01-5
.)

LT Diagnosis
HELP
Select function XX
Display:

Press the keys 0 and 8 for the function "Read measurement value block" and confirm the input using the Q key.

Reading measurement value block
HELP
Enter display group number XXX
Display:

Press the keys 0;0 and 5 for the "Display group number 005" and confirm the input using the Q key.

Read measurement values block 5
⇒
1
2
3
4
Display:
(1...4 = display fields)

Read off the intake air temperature value in display field 3.
Setpoint value: at least 11.0 V
Press the ⇒key.
Press the keys 0 and 6 for the function "Quit output" and confirm the input using the Q key.

Switch the ignition off.

If the setpoint value is not reached:

Connect test box V.A.G 1598/26 => Page
01-71
.

Check the power supply at terminal 30

Measure supply voltage between Sockets 1 (red) + 10 (red) of test box with multimeter and auxiliary cables from V.A.G 1594:
Setpoint value: at least 11.0 V

If the setpoint value is not reached:

Check the cable connections to the central electrical system according the current flow diagram:

=> Current flow diagrams, Electrical fault finding and Fitting locations

Check the power supply at terminal 15

Connect multimeter between Sockets 1 (red) + 2 (red) of test box with auxiliary cables from V.A.G 1594 for voltage measurement.
Switch on ignition.
Setpoint value: at least 11.0 V

If the setpoint value is not reached:

Check the cable connections to the central electrical system according the current flow diagram:

=> Current flow diagrams, Electrical fault finding and Fitting locations

Disconnect test box V.A.G 1598/26 => Page
01-71
, Connecting test box V.A.G 1598, Disconnecting test box.